Abstract

A new method is employed to obtain the temperatures of highly charged carbon ions in the boundary layer of tokamak discharges. The lithium-beam activated charge-exchange spectroscopy is used to measure spectral profiles of lines in the visible region excited by electron transfer between impurity ions and a fast neutral lithium diagnostic beam. Assuming a Maxwellian velocity distribution of the ions, temperatures are deduced by fitting a Gaussian profile to the Doppler broadened emission lines. The method is capable of investigating different heating scenarios, including ohmic discharges, beam-heated and high-frequency-heated plasmas, as well as combinations thereof. Furthermore, the relatively high cross-section of charge-exchange between neutral lithium and carbon ions allows the use of a narrow beam diameter and a low current density, so that strictly local measurements of ion temperatures can be performed without changing plasma conditions by the diagnostic experiment itself. In this paper, radial temperature profiles of the fully stripped C(6+) are investigated. These have been obtained, with and without additional NI-beam-heating in the outmost 20 cm of TEXTOR plasmas, using the neutral lithium diagnostic beam for the first time.